Recurrent herpetic keratitis is a major cause of corneal blindness in the Western world. Affected individuals are otherwise healthy, productive members of society. The problem is not acute epithelial disease but alterations in corneal structure and function which occur as a result of recurrent episodes of disease. Current therapy cannot prevent establishment of latent infection or recurrent disease with its known sequellae. Although much has been learned regarding herpes virus latency, the fundamental issue of the state of the viral genome and its relationship to the host has not been resolved. Definition of herpes virus latency at the molecular level is prerequisite to determining how latency is initiated and reversed, thus leading to intervention or interruption of this relentless cycle. The previous project has allowed us to develop and characterize a model for latent and recurrent herpes simplex keratitis which closely mimics human disease. Recently, we began to investigate latency at the molecular level in this model. The isolation of two species of DNA from ganglia of latently infected animals raises the possibility of the simultaneous co-existance of both latent and persisting HSV infection. The specific intent of this project is to characterize latency and reactivation at the molecular level in a model that mimics human disease. Part I of this proposal is designed to investigate the state of the viral genoma during latency and its relationship to the host. Plasmids will be utilized to amplify viral DNA isolated during latent infection so that it can be characterized and sequenced. Activity of the viral genome during latency will be evaluated by mRNA hybridization and protein labeling studies. Part II of this proposal is designed to investigate reactivation by multivariant analysis of strain-specific DNA variations between HSV-1 strains exhibiting a known spectrum of clinical disease and reactivation potential. These studies will allow for identification of specific genome regions responsible for reactivation which will be cloned and utilized for transfection experiments. Cloned segments resulting in desired biological activity will be characterized and sequenced. Basic knowledge concerning mechanisms of herpes virus latency and reactivation will provide the basis for appropriate therapeutic intervention (antiviral/immunological) in this devastating disease process.